In a wide variety of circumstances, animals, including humans, can suffer from bleeding due to wounds or during surgical procedures. In some circumstances, the bleeding is relatively minor, and normal blood clotting functions in addition to the application of simple first aid are all that is required. In other circumstances substantial bleeding can occur. These situations usually require specialized equipment and materials as well as personnel trained to administer appropriate aid.
In an effort to address the above-described problems, materials have been developed for controlling excessive bleeding. Topical Absorbable Hemostats (TAHs) are widely used in surgical applications. TAHs encompass products based on oxidized cellulose (OC), oxidized regenerated cellulose (ORC), gelatin, collagen, chitin, chitosan, etc. To improve the hemostatic performance, scaffolds based on the above materials can be combined with biologically-derived clotting factors, such as thrombin and fibrinogen.
The control of bleeding is essential and critical in surgical procedures to minimize blood loss, to reduce post-surgical complications, and to shorten the duration of the surgery in the operating room. Due to its biodegradability and its bactericidal and hemostatic properties, oxidized cellulose, as well as oxidized regenerated cellulose has long been used as a topical hemostatic wound dressing in a variety of surgical procedures, including neurosurgery, abdominal surgery, cardiovascular surgery, thoracic surgery, head and neck surgery, pelvic surgery and skin and subcutaneous tissue procedures. A number of methods for forming various types of hemostats based on oxidized cellulose materials are known, whether made in powder, woven, non-woven, knit, and other forms. Currently utilized hemostatic wound dressings include knitted or non-woven fabrics comprising oxidized regenerated cellulose (ORC), which is oxidized cellulose with increased homogeneity of the cellulose fiber. Examples of such hemostatic wound dressings commercially available include SURGICEL® resorbable hemostat; SURGICEL® NU-KNIT® resorbable hemostat; SURGICEL® FIBRILLAR resorbable hemostat, and SURGICEL® SNoW™ resorbable hemostat; all available from Johnson & Johnson Wound Management Worldwide, a division of Ethicon, Inc., Somerville, N.J., a Johnson & Johnson Company. Other examples of commercial resorbable hemostats containing oxidized cellulose include GelitaCel® resorbable cellulose surgical dressing from Gelita Medical BV, Amsterdam, The Netherlands. The commercially available oxidized cellulose hemostats noted above are knitted or nonwoven fabrics having a porous structure for providing hemostasis.
U.S. Pat. No. 3,364,200 to Ashton and Moser describes a resorbable, surgical hemostat in the form of pledgets of integrated oxidized cellulose staple fibers.
Published U.S. Patent Application Publication 2008/0027365 to Huey describes an apparatus for promoting hemostasis utilizing oxidized cellulose in the form of a compressible, shapeable mass that is formed into a sheet for placement on a bleed site and further having a sleeve in a form of a tubular shell dimensioned to receive a limb.
Published U.S. Patent Application Publication 2004/0005350 to Looney et al. discloses hemostatic wound dressings utilizing a fibrous fabric substrate made from carboxylic-oxidized cellulose and containing a porous, polymeric matrix homogeneously distributed through the fabric and made of a biocompatible, water-soluble or water-swellable cellulose polymer, wherein the fabric contains about 3 percent by weight or more of water-soluble oligosaccharides.
Patent publication WO 2007/076415 by Herzberg et al. and entitled “COMPOSITIONS AND METHODS FOR PREVENTING OR REDUCING POSTOPERATIVE ILEUS AND GASTRIC STASIS”, discloses milling of ORC, particularly cryogenic milling, using a cutting blade of a motor-driven mill.
An article titled “The Ball-Milling of Cellulose Fibers and Recrystallization Effects”, Journal of Applied Polymer Science, Volume 1 Issue 3, Pages 313-322, (1959) by Howsmon and Marchessault, reports results of a study of the effect of fine structure on the decrystallization process which results from the ball-milling of cellulose. The rate of decrystallization is sensitive to the type of fine structure and is accelerated by the presence of moisture. The extent of chain degradation was greater in air atmosphere than in carbon dioxide, suggesting that mechanically induced free radical degradation occurs along with other chain-breaking processes. A study of the density and moisture regain of the samples after various times of milling showed that a linear relation between regain and density held over the entire range studied. The relation was the same for native and regenerated cellulose. The process of recrystallization of the ball-milled samples was studied under various conditions and compared to the hydrolytically induced recrystallization of rayons. The reference discloses effect of fine structure on the decrystallization process which results from the ball-milling of cellulose fibers.
U.S. Pat. No. 6,627,749 discloses a process for grinding oxidized cellulose using a pestle and mortar or in a ball mill or any other conventional laboratory grinder. It further discloses that when cotton linter sheet is used as the starting cellulose source, the fiber length of the product decreases with increasing reaction time. When ball-milled, the long fibrous structures of the product turn into smaller fibers, to loosely-packed spherical aggregates. No significant change in the crystallinity of these samples occurs as a result of ball milling. The reference discloses long fibrous oxidized cellulose ball milled to form small fibers or loosely packed spherical aggregates.
Other related references include: U.S. Pat. No. 6,309,454, Freeze-dried composite materials and processes for the production thereof; U.S. Pat. Nos. 5,696,191; 6,627,749; 6,225,461 to Kyoko et al.; PCT patent publication WO2001/024841 A1, Compositions for the Treatment of Wound Contracture; and European patent publication EP1,323,436 to Dae Sik et al.
Other related references include: An article titled “The role of oxidized regenerated cellulose/collagen in chronic wound repair and its potential mechanism of action”, The International Journal of Biochemistry & Cell Biology 34 (2002) 1544-1556, Breda Cullen et al.; an article by Rangam et al. teaching methods of making silk powders through milling processes [Powder Technology 185 (2008), p 87-95]; an article by Yasnitskii et al., Oxycelodex, a new hemostatic preparation, Pharmaceutical Chemistry Journal, 18, 506-5; discloses an Oxycelodex paste that consists of two components, oxidized cellulose powder and a 20% aqueous solution of dextran.
U.S. Patent Application 2006/0233869 to Looney et al. discloses using a chopping/shredding process to make ORC micro-fibers from ORC fabrics. The rod-like shaped fibers had sizes which ranged from about 35 to 4350 micrometers.